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Sticky droplets raining down from Magnolia trees

Editor’s note: This article is from the archives of the MSUCrop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
included.

The
honeydew excretions from Magnolia scale can make a mess of cars or bikes
parked under them. Also, yellow jackets are attracted to the sugary
honeydew. Finally, if there is enough scale, the foliage and branches
under the scales may start to turn black from sooty mold fungus growing
on the honeydew. All of this is a result of a heavy infestation of one
of our largest soft scales in North America – Magnolia scale. The young scales present now are covered with a white powder. Later in
the summer they will turn dark brown. Unfortunately, they have been very
difficult to control with insecticides. Some arborists have used Merit
(imidacloprid) soil drenches each April or May with spotty records of
success. The imidacloprid drenches will probably take two years before
being effective, and not even that is guaranteed. Meanwhile, spraying is
the only remaining option (other than replacing the trees). Talstar has
been effective on most of the soft scale insects, but in this case, you
will probably need two applications two weeks apart starting at this
time to make a good dent in the infestation. Some of the new
neonicotinoid insecticides have been very effective on soft scales and
mealybugs. You may want to try foliar sprays of Flagship, Safari, or
Tristar for Magnolia scale, cottony maple scale or other troublesome
soft scale insects.